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HIGH

CVE-2025-21704

CVSS v3

7.8

HIGH

EPSS Score

0.4 %

exploit probability, as of 2026-10-19

CISA KEV

No

known exploited

Exploitation

—

SSVC status

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Affected and fixed versions

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • linux-awsUbuntu:24.10all versions · fixed in 6.11.0-1014.15

Vendor advisories

  • CVE-2025-21704 Red Hat Product Security90 known affected

    kernel: Linux kernel: usb: cdc-acm: Memory corruption due to improper buffer size check

    kernel as a component of Red Hat Enterprise Linux 6 · kernel-abi-whitelists as a component of Red Hat Enterprise Linux 6 · kernel-bootwrapper as a component of Red Hat Enterprise Linux 6

  • SSA-784472 Siemens ProductCERT1 known affected

    SSA-784472: Vulnerabilities in the additional GNU/Linux subsystem of the SIMATIC S7-1500 TM MFP V1.1.1

    SIMATIC S7-1500 TM MFP - GNU/Linux subsystem

  • ICSA-24-102-01 CISA1 known affected

    Siemens SIMATIC S7-1500 TM MFP

    SIMATIC S7-1500 TM MFP - GNU/Linux subsystem

  • SSA-265688 Siemens ProductCERT1 known affected

    SSA-265688: Vulnerabilities in the additional GNU/Linux subsystem of the SIMATIC S7-1500 TM MFP V1.1

    SIMATIC S7-1500 TM MFP - GNU/Linux subsystem

Full record on NVD

Description

In the Linux kernel, the following vulnerability has been resolved: usb: cdc-acm: Check control transfer buffer size before access If the first fragment is shorter than struct usb_cdc_notification, we can't calculate an expected_size. Log an error and discard the notification instead of reading lengths from memory outside the received data, which can lead to memory corruption when the expected_size decreases between fragments, causing `expected_size - acm->nb_index` to wrap. This issue has been present since the beginning of git history; however, it only leads to memory corruption since commit ea2583529cd1 ("cdc-acm: reassemble fragmented notifications"). A mitigating factor is that acm_ctrl_irq() can only execute after userspace has opened /dev/ttyACM*; but if ModemManager is running, ModemManager will do that automatically depending on the USB device's vendor/product IDs and its other interfaces.

Technical details

Published
2025-02-22

Frequently asked questions

What is CVE-2025-21704?

In the Linux kernel, the following vulnerability has been resolved: usb: cdc-acm: Check control transfer buffer size before access If the first fragment is shorter than struct usb_cdc_notification, we can't calculate an expected_size. Log an error and discard the notification instead of reading lengths from memory outside the received data, which can lead to memory corruption when the expected_size decreases between fragments, causing `expected_size - acm->nb_index` to wrap. This issue has been present since the beginning of git history; however, it only leads to memory corruption since commit ea2583529cd1 ("cdc-acm: reassemble fragmented notifications"). A mitigating factor is that acm_ctrl_irq() can only execute after userspace has opened /dev/ttyACM*; but if ModemManager is running, ModemManager will do that automatically depending on the USB device's vendor/product IDs and its other interfaces.

Is CVE-2025-21704 actively exploited?

Active exploitation of CVE-2025-21704 has not been confirmed. Its EPSS score was 0.4% on 2026-10-19, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2025-21704?

CVE-2025-21704 has a CVSS v3 base score of 7.8 (HIGH severity).

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